Conventionally, in Patent Document 1, a scroll-type compressor is disclosed as a compressor used for a so-called gas injection cycle (economizer refrigeration cycle), and includes a low-stage scroll compression mechanism (hereinafter, described as a low-stage compression mechanism), and a high-stage scroll compression mechanism (hereinafter, described as a high-stage compression mechanism). The compressor pressurizes a refrigerant (fluid) in multiple stages in these multiple compression mechanisms.
Like the scroll-type compressor of Patent Document 1, in a compressor including multiple compression mechanisms, a size of the compressor is likely to be large as a whole. With respect to this, the scroll-type compressor of Patent Document 1 adopts a movable scroll in which a spiral-shaped tooth portion is provided on both side of a flat-shaped substrate portion in an axial direction. Since a low-stage compression mechanism and a high-stage compression mechanism are positioned in proximity to the opposite sides of the movable scroll in the axial direction, the size of the compressor is reduced as a whole.
Further, in the scroll-type compressor of Patent Document 1, a rotation shaft which transmits a rotational drive force to the movable scroll is disposed to penetrate through a center part of the movable scroll, and both end parts of the rotation shafts are supported rotatably.
In such configuration where the both end sides of the rotation shaft is rotatably supported, a largest rotation rate below which the rotation shaft is rotatable stably can be increased more than a configuration where only a one side of the rotation shaft is rotatably supported. Hence, a maximum volume of a compression chamber of each compression mechanism required for discharging a fluid at a desired flow rate can be decreased, and thus the size can be further reduced.
However, like the scroll-type compressor of Patent Document 1, in the configuration where the rotation shaft extends through the center part of the movable scroll, an energy loss may increase as a whole.
In more detail, in a general scroll compression mechanism in which a rotation shaft does not extend through a center part of a movable scroll, multiple crescent-shaped compression spaces are provided in a gap between a spiral-shaped movable tooth portion provided on the movable scroll and a spiral-shaped fixed tooth portion provided on a fixed scroll when viewed in an axial direction of the rotation shaft. The multiple crescent-shaped compression spaces constitute a compression chamber.
Moreover, these multiple compression spaces are positioned symmetrically with respect to a shaft center of the rotation shaft, and swirl and shift from a radially outer side to a radially inner side with reducing in volume in accordance with revolution motion of the movable scroll. When two compression spaces provided at positions symmetric about the shaft center move to an innermost side (shaft center side), the two compression spaces communicates with each other, and fluid compressed in the two compression spaces is discharged from a discharge hole provided on a center part of the fixed scroll.
However, like the scroll-type compressor of Patent Document 1, in a configuration where a rotation shaft is disposed to extend through a center part of a movable scroll, two compression spaces cannot be made to communicate with each other, or a discharge hole cannot be provided on a center part. Thus, in order to discharge fluids pressurized in respective compression spaces, the fluids pressurized in the respective compression spaces have to be joined together before the multiple compression spaces move to the shaft center side.
In this case, if a pressure difference is generated between the fluids pressurized in the respective compression spaces, the fluid may flow backward from a high-pressure side compression space to a low-pressure side compression space, and an energy loss of the compressor may increase. To limit the backward flow, if a special communication passage or the like, through which the respective compression spaces communicate with each other when fluid pressures in the multiple compression spaces becomes equivalent to each other, is provided, an inner configuration inside the compressor may become complicated.